It has long been known that students' self efficacy can influence their performance of assessments. I conducted a study to investigate the relationship between students' predicted performance and actual performance on five exams in a second-semester calculus-based physics class. After completion of each of the five exams during the semester, students in the class were given about 72 hours to predict their individual and class mean score on the exam. As incentive, students were offered extra credit worth 1% of the exam points for each predicted score that was correct within 1% of the actual score. I compared students' individual and mean score predictions with the actual scores to investigate the relationship between prediction accuracies and exam performance of the students. I also examined trends in the prediction accuracies of students over the five exams. I report on the results and possible implications of this study.